Process of making screws and bolts



May 5, 1931 U N I 1,803,8Q3

PROCESS OFMAKING SCREWS Ann BOLTS Filed Feb. 3, 1930 1 1 2. 7 70- 9 I I L /0 JG: u enfozs fect upon the molecular structure of the Patented May 5, 1931 UNITE ica CHARLES KAUFMAN, or GARFIELD HEIGHTS, onro Application filed February 3, 1930. Serial No. 425,408.

This invention relates to a process of making bolts and screws, particularly a process of forming such articles by drawing up and heading lengths of round stock. In some 5 of its aspects the present invention is an improvement over the process described in my Letters Patent No. 1,617,122, dated Februmy 8, 1927.

In the heading of bolt and screw blanks by the upsetting process, it has been the practice usually, that is prior to the invention of the above mentioned patent,to form the head by working it up in a series of upsetting steps from wire of the pitch diameter of the threaded portion of the article. .Usually a sort of collar is formed upon the stock at 'a position spaced from one end thereof and thereafter the stock beyond the collar is compressed and expanded radially by another upsetting operation. When this is done the metal of these two partsof the head does not flow together and become an entirely homogeneous whole, as it should do if the head is to have maximum strength. On the contrary the stock beypnd the collar is folded down, as it were,*against the collar, leaving an annular joint which marks a cleavage plane whenever the head is subjected to heavy strains. Furthermore the strains in the metal of the head caused by upsetting increase as the degree of enlargement increases. I

- Accordingly it is an object of the present invention to reduce the liability of fracture in the upset heads of bolts and screws by eliminating any foliated structure therein and by decreasing heading strains.

In accordance with the method of the present invention the stock is subjected to two drawing operations to reduce the diameter first to the overall diameter of the threads of the finished article, and secbnd to reduce the major part of the first reduced portion to the pitch diameter of the threads,.these reducing operations having a beneficial efmetal affected. Then the unreduced portion of the stock is upset to form the head of 1. the article, although I prefer to perform this upsetting operation simultaneously with one of the drawing operations, preferably the last one. There is but one upsetting blow necessary, inasmuch as the original stock is overall diameter of the threads. In the patented process there is butone drawing operation necessary, but the upsetting requires two blows. Hence the number of operations in the present process isnot increased over those employed in my patented process, and the present process employs more reduction than upsetting, which, as before stated, is of advantage in its action upon the metal structure, thereby resulting in a stronger article.

In the accompanying drawing, wherein I have illustrated one embodiment of the invention for the purposes of the present application,

Figs. 1 and 2 are side and end elevations of a length of stock constituting the material -with which the process begins.

Figs. 3 and 4 arev similar views after the first drawing operation.

Figs. 5 and 6 are similar views after the second operation, wherein the upsetting 'of the head is performed simultaneously with the final drawing of the shank.

Figs. 7 and 8 are similar views of the completed article, that is after it is threaded and the head is trimmed.

Fig. -9 is a cross sectional View showing the die and hammer employed for the first drawing operation, with a length of material in the position and form which it assumes at the end of the hammer stroke, and Fig. 10 is a view similar to Fig. 9, showing the corresponding parts at the end of the second or combined upsetting and drawing operation.

The present invention may be used advantageously forming practically all kinds of screws and bolts without regard tothe shape of the heads thereof. In carrying out the invention I employ round wire stock of indefinite length, which is cut by suitable means to a predetermined length 10, as in dicated in Fig. 1. This length of stock 10 is then fed into a cold heading machine of any suitable design, being-caused to enter an opening 11 in=a die 12, this opening being of the same or substantially the same diameter as the stock 10. Aligned and communicating with the opening 11 in the die is a further opening 13 of smaller diameter. The hammer 14 of the machine forces the stock into the opening 13ydrawin down the major portion of the stock to a diameter 15,

and thereby also lengthening the article somewhat. The blank is now in the condition illustrated in Fig. 3, where the portion 10a is of the same diameter as original stock 10.

The blank is next fed into another cold heading machine, or into other .dies inthe same machine, and the reduced diameter portion15 is caused to enter an opening 16 in a die 17 this opening being of the same or substantially-the same diameter as the portion 15 of the blank. Communicating with the opening 16 is an aligned opening 18 of reduced diameter. The opening 16 also communicates with an enlarged opening 19, which registers substantially with a socket or opening 20 in a hammer 21 which cooperates with the die 17 When thehammer 21 strikes, the greater part of the portion 15 of the blank is caused to enter the opening 18, and is thereby drawn down to a diameter 22. A part of the portion -15 however is' unaffected, and remains as the portion 15a,

shown in Fig. 5. At the sametime that thls second reduction is taking place the portlon 10w of the blank is" being upset ta 11 the openings 19 and 20, resulting in a head 23.

Rods 24 and 25, shown in Figs. 9 and 10,

are ejectors which may be employed for stripping the blank from the dies 12 and 17 respectively after the hammers have struck and receded. 1 When the blank is finished to the extent illustrated in Fig. 5,: it then remains to trim the head 23 to the desired form such, for instance, as the hex 23aillustrated in Figs. 7 and 8, and. to roll or otherwise form the. threads 24 in the portion 22 of the blank.

The parts 10 and 10a are of the same diameter, the parts 15 and 150 are alsotof the same diameter, and the part 22 'is of the pitch diameter of the screw threads The reduction of original stock by drawing down to the diameters 15 and 22, serves to compact and harden the metal, particularly that near the surface. The increase in diameter of the head 23 over that of stock 10 or 12a blanks, which comprises red'ucin 1,sos,aoa

is one of relatively small degree, and may be performed by a sin le blow, thus removing entirely any possibility of foliated structure, and lessening the danger of fracture due to heading strains in the metal.

While in the foregoing description and in the accompanying drawing I have disclosed my method in considerable detail, I desire it to be understood that such detail disclosure has been resorted to primarily for the purpose of fully illustrating the invention in conformity with the requirements of the statute, and is not to be construed as amounting to a limitation upon the scope thereof.

Having thus described my invention, I claim 1. blanks which comprises drawing a portion of a length of stock of cross-sectional area greater than that of the shank of the blank to form a round cross section of a diameter equal to the overall diameter (if the threads of the finishedarticle, drawing .down a por tion of said round cross section to a diameter equal to the pitch diameter of the threads, and upsettm the unreduced portion of the stock to orm a head.

' ,2. The method of making bolt and screw blanks which comprises drawing a portion of a length of stock of. cross-sectional area greater than that of the shank of the blank to form a round cross section of a diameter ther operation drawin 'fihe method of making bolt and screw v said reduced section st ll further to a diametei' equal to the pitch diameter of the thread, and at the same time upsetting the. Enrgduced portion of the stock to form a ea a 4. The method of making bolt and screw 0 p. y step .by means of a plurality of drawing operatlons a portion of a length of stock 0 cross-sectional area greater than that of the shank of the blank until the desired minimum diameter of the blank is reached, and

upsettm the unreducedportion of stock to X form a ead.

' In testimony whereof, I hereunto afiix my signature. t CHARLES KAUFMANL 

